Open vessel sealing instrument

ABSTRACT

A disposable open electrosurgical forceps for sealing tissue is disclosed in the present disclosure. The disposable open electrosurgical forceps comprise a pair of first and second shaft members containing a fiber reinforced thermoplastic blend material having fiber strands of at least 2 millimeters in length. Each shaft member includes a jaw member disposed at a distal end thereof which are movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp tissue therebetween. Each of the jaw members also includes an electrically conductive sealing plate for communicating electrosurgical energy through tissue held therebetween. At least one of the jaw members includes a knife channel defined along a length thereof which is dimensioned to reciprocate a cutting mechanism therealong. An actuator is included for selectively advancing the cutting mechanism from a first position wherein the cutting mechanism is disposed proximal to tissue held between the jaw members to at least one subsequent position wherein the cutting mechanism is disposed distal to tissue held between the jaw members. The actuator includes a trigger which cooperates with a rack and pinion system to advance the cutting mechanism from the first to second positions through tissue held therebetween.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. ProvisionalApplication Ser. No. 60/643,804 entitled “OPEN VESSEL SEALINGINSTRUMENT” filed on Jan. 14, 2005, the entire contents of which areincorporated by reference herein.

BACKGROUND

The present disclosure relates to forceps used for open surgicalprocedures. More particularly, the present disclosure relates to adisposable open forceps which seals and severs tissue along a tissueseal.

TECHNICAL FIELD

A forceps is a plier-like instrument which relies on mechanical actionbetween its jaws to grasp, clamp and constrict vessels or tissue.So-called “open forceps” are commonly used in open surgical procedureswhereas “endoscopic forceps” or “laparoscopic forceps” are, as the nameimplies, used for less invasive endoscopic surgical procedures.Electrosurgical forceps (open or endoscopic) utilize both mechanicalclamping action and electrical energy to effect hemostasis by heatingtissue and blood vessels to coagulate and/or cauterize tissue.

Certain surgical procedures require more than simply cauterizing tissueand rely on the unique combination of clamping pressure, preciseelectrosurgical energy control and gap distance (i.e., distance betweenopposing jaw members when closed about tissue) to “seal” tissue, vesselsand certain vascular bundles.

Vessel sealing or tissue sealing is a recently-developed technologywhich utilizes a unique combination of radiofrequency energy, pressureand gap control to effectively seal or fuse tissue between two opposingjaw members or sealing plates. Vessel or tissue sealing is more than“cauterization” which involves the use of heat to destroy tissue (alsocalled “diathermy” or “electrodiathermy”). Vessel sealing is also morethan “coagulation” which is the process of desiccating tissue whereinthe tissue cells are ruptured and dried. “Vessel sealing” is defined asthe process of liquefying the collagen, elastin and ground substances inthe tissue so that the tissue reforms into a fused mass withsignificantly-reduced demarcation between the opposing tissuestructures.

In order to effectively “seal” tissue or vessels, two predominantmechanical parameters must be accurately controlled: 1) the pressure orclosure force applied to the vessel or tissue; and 2) the gap distancebetween the conductive tissue contacting surfaces (electrodes). As canbe appreciated, both of these parameters are affected by the thicknessof the tissue being sealed. Accurate application of pressure isimportant for several reasons: to reduce the tissue impedance to a lowenough value that allows enough electrosurgical energy through thetissue; to overcome the forces of expansion during tissue heating; andto contribute to the end tissue thickness which is an indication of agood seal. It has been determined that a good seal for certain tissuesis optimum between about 0.001 inches and about 0.006 inches.

With respect to smaller vessels or tissue, the pressure applied becomesless relevant and the gap distance between the electrically conductivesurfaces becomes more significant for effective sealing. In other words,the chances of the two electrically conductive surfaces touching duringactivation increases as the tissue thickness and the vessels becomesmaller.

Commonly owned, U.S. Pat. No. 6,511,480, PCT Patent Application Nos.PCT/US01/11420 and PCT/US01/11218, U.S. patent application Ser. Nos.10/116,824, 10/284,562 and 10/299,650 all describe various open surgicalforceps which seal tissue and vessels. All of these references arehereby incorporated by reference herein. In addition, several journalarticles have disclosed methods for sealing small blood vessels usingelectrosurgery. An article entitled Studies on Coagulation and theDevelopment of an Automatic Computerized Bipolar Coagulator, J.Neurosurg., Volume 75, July 1991, describes a bipolar coagulator whichis used to seal small blood vessels. The article states that it is notpossible to safely coagulate arteries with a diameter larger than 2 to2.5 mm. A second article is entitled Automatically Controlled BipolarElectrocoagulation—“COA-COMP”, Neurosurg. Rev. (1984), pp. 187-190,describes a method for terminating electrosurgical power to the vesselso that charring of the vessel walls can be avoided.

Typically and particularly with respect to open electrosurgicalprocedures, once a vessel is sealed, the surgeon has to remove thesealing instrument from the operative site, substitute a new instrumentand accurately sever the vessel along the newly formed tissue seal. Ascan be appreciated, this additional step may be both time consuming(particularly when sealing a significant number of vessels) and maycontribute to imprecise separation of the tissue along the sealing linedue to the misalignment or misplacement of the severing instrument alongthe center of the tissue sealing line.

Many endoscopic vessel sealing instruments have been designed whichincorporate a knife or blade member which effectively severs the tissueafter forming a tissue seal. For example, commonly-owned U.S.application Ser. Nos. 10/116,944 and 10/179,863 describe one suchendoscopic instrument which effectively seals and cuts tissue along thetissue seal. Other instruments include blade members or shearing memberswhich simply cut tissue in a mechanical and/or electromechanical mannerand are relatively ineffective for vessel sealing purposes.

Open vessel sealing instruments have also been designed whichincorporate a knife or blade member which effectively severs the tissueafter forming a tissue seal. For example, commonly-owned U.S.application Ser. No. 10/873,860 describes on such open vessel sealinginstrument.

The vessel sealing instruments of the prior art are typicallyconstructed such that the instruments are re-usable. Typically, theshaft members are made of stainless steel or other surgical steel. Theexpense of this material makes it somewhat impractical for theinstruments to be disposable.

Thus, a need exists to develop a more cost effective disposable Besselsealing forceps which can seal vessels and tissue consistently andeffectively. Moreover, a need also exists to develop a disposable vesselsealing forceps which can both seal vessels and tissue as well as allowthe surgeon the option of selectively cutting the tissue after that sealis formed.

SUMMARY

The present disclosure relates to a disposable open electrosurgicalforceps for sealing tissue including a pair of first and second shaftmembers containing a fiber reinforced thermoplastic blend materialhaving fiber strands of at least 2 millimeters in length. Each shaftmember includes a jaw member disposed at a distal end thereof which aremovable from a first position in spaced relation relative to one anotherto at least one subsequent position wherein the jaw members cooperate tograsp tissue therebetween. Each of the jaw members include anelectrically conductive sealing plate for communicating electrosurgicalenergy through tissue held therebetween. At least one of the jaw membersincludes a knife channel defined along a length thereof, the knifechannel is dimensioned to reciprocate a cutting mechanism therealong. Anactuator is alos included which operatively connects to one of the shaftmembers and is configured to selectively advance the cutting mechanismfrom a first position wherein the cutting mechanism is disposed proximalto tissue held between the jaw members to at least one subsequentposition wherein the cutting mechanism is disposed distal to tissue heldbetween the jaw members. The actuator has a trigger which cooperateswith a rack and pinion system to advance the cutting mechanism from thefirst to second positions through tissue held therebetween.

In one embodiment, the forceps includes a knife channel defined along alength of one of the sealing plates which is dimensioned to reciprocatea cutting mechanism therealong.

In a further embodiment of the present disclosure, the fiber reinforcedthermoplastic blend material is a blend of at least one firstthermoplastic resin material and at least one second thermoplastic resinmaterial. At least one first thermoplastic resin material ispolycarbonate. At least one second thermoplastic resin material isacrylonitrile-butadiene-styrene. The fiber reinforced thermoplasticblend material may be a blend of polycarbonate andacrylonitrile-butadiene-styrene.

In another embodiment of the present disclosure, the fiber reinforcedthermoplastic blend material contains glass fiber. The fiber reinforcedthermoplastic blend material contains glass fiber present in an amountof about 40% by volume of the total volume of the blend.

Yet a further embodiment of the present disclosure includes a disposableopen electrosurgical forceps for sealing tissue having a pair of firstand second shaft members containing a glass fiber reinforced blend ofpolycarbonate resin material and acrylonitrile-butadiene-styrene resinmaterial wherein the glass fiber is present at 40% by volume of thetotal volume of the blend.

Each shaft member includes a jaw member disposed at a distal end thereofwhich are movable from a first position in spaced relation relative toone another to at least one subsequent position wherein the jaw memberscooperate to grasp tissue therebetween. Each of the jaw members includesan electrically conductive sealing plate for communicatingelectrosurgical energy through tissue held therebetween.

The forceps includes a knife channel defined along a length of one ofthe sealing plates is dimensioned to reciprocate a cutting mechanismtherealong.

Also included in the forceps is an actuator operatively connected to oneof the shaft members which is configured to selectively advance thecutting mechanism from a first position wherein the cutting mechanism isdisposed proximal to tissue held between the jaw members to at least onesubsequent position wherein the cutting mechanism is disposed distal totissue held between the jaw members. The actuator includes a triggerwhich cooperates with a rack and pinion system to advance the cuttingmechanism from the first to second positions through tissue heldtherebetween.

The present disclosure also relates to a disposable open electrosurgicalforceps for sealing tissue which includes a pair of first and secondshaft members containing a glass fiber reinforced blend of polycarbonateresin material and acrylonitrile-butadiene-styrene resin material havingglass fibers in the range of about 2 millimeters to about 11 millimetersin length. The glass fibers are present at 40% by volume of the totalvolume of the blend.

Each shaft member includes a jaw member disposed at a distal endthereof, at least one of the jaw members being movable from a firstposition in spaced relation relative to one another to at least onesubsequent position wherein the jaw members cooperate to grasp tissuetherebetween. Each of the jaw members also includes an electricallyconductive sealing plate which communicates electrosurgical energythrough tissue held therebetween. At least one of the jaw members has aknife channel defined along a length thereof which is dimensioned toreciprocate a cutting mechanism therealong.

An actuator is included which operatively connects to one of the shaftmembers and which is configured to selectively advance the cuttingmechanism from a first position wherein the cutting mechanism isdisposed proximal to tissue held between the jaw members to at least onesubsequent position wherein the cutting mechanism is disposed distal totissue held between the jaw members. The actuator includes a triggerwhich cooperates with a rack and pinion system to advance the cuttingmechanism from the first to second positions through tissue heldtherebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1 is a left, perspective view of an open forceps with a cuttingmechanism according to the present disclosure;

FIG. 2 is a left, side view of the forceps of FIG. 1;

FIG. 3 is an internal, perspective view of the forceps of FIG. 1 showinga rack and pinion actuating mechanism for advancing the cuttingmechanism and a series of internally disposed electrical connections forenergizing the forceps;

FIG. 4 is an internal, side view of the forceps showing the rack andpinion actuating mechanism and the internally disposed electricalconnections;

FIG. 5 is an enlarged, perspective view showing the area of detail inFIG. 3;

FIG. 6 is an enlarged, perspective view showing the area of detail inFIG. 3;

FIG. 7 is a perspective view of the forceps of FIG. 1 with partsseparated;

FIG. 8 is a perspective view of one shaft of the forceps of FIG. 1;

FIG. 9 is an enlarged, perspective view showing the area of detail inFIG. 8;

FIG. 10 is an enlarged, perspective view of the cutting mechanism;

FIG. 11 is a side cross section along lines 11-11 of FIG. 10;

FIG. 12 is an enlarged, perspective view of the area of detail in FIG.10;

FIG. 13 is a greatly-enlarged perspective view of a distal electricalconnector of the forceps of FIG. 1;

FIG. 14 is an enlarged, left perspective view of the one of the jawmembers of the forceps of FIG. 1;

FIG. 15 is an enlarged, right perspective view of the jaw member of FIG.14;

FIG. 16 is side cross sectional view showing the forceps in openconfiguration for grasping tissue;

FIG. 17 is a side cross sectional view showing the area of detail inFIG. 16;

FIG. 18 is a rear, perspective view of the forceps of FIG. 1 showngrasping tissue with a ratchet mechanism shown prior to engagement;

FIG. 19 is a rear view of the forceps of FIG. 1 showing the ratchetmechanism engaged;

FIG. 20 is a greatly-enlarged, side cross sectional view showing theforceps in a closed position and defining a gap distance “G” betweenopposing jaw members;

FIG. 21 is a greatly-enlarged, perspective view of a tissue seal;

FIG. 22 is a side cross sectional view taken along line 22-22 of FIG.21;

FIG. 23 is a side cross sectional view showing the forceps in a closedposition and showing the activation and advancement of the cuttingmechanism;

FIG. 24 is an enlarged view of the area of detail in FIG. 24; and

FIG. 25 is a greatly-enlarged, cross sectional view showing tissueseparated along the tissue seal after advancement of the cuttingmechanism.

DETAILED DESCRIPTION

The present disclosure relates to an electrosurgical forceps which isconstructed of a fiber reinforced thermoplastic. Fiber reinforcedthermoplastics are materials which provide high strength, highstiffness, and a highly predictable mode of pressure transmission,particularly in a hemostat application wherein applied tissue pressureis critical. Additionally, the use of a fiber reinforced thermoplasticenables a cost-effective electrosurgical forceps to be made which isdisposable. Disposable electrosurgical forceps eliminate the need tosterilize and re-use the instruments.

Referring now to FIGS. 1-7, a forceps 10 for use with open surgicalprocedures includes elongated shaft portions 12 a and 12 b each having aproximal end 14 a, 14 b and a distal end 16 a and 16 b, respectively. Inthe drawings and in the descriptions which follow, the term “proximal”,as is traditional, will refer to the end of the forceps 10 which iscloser to the user, while the term “distal” will refer to the end whichis further from the user.

Elongated shaft portions 12 a and 12 b are constructed of the fiberreinforced thermoplastic material. The fiber reinforced material is ablend of a first thermoplastic resin material and a second thermoplasticrein material wherein the blend contains a reinforcing fiber.

Generally, the first thermoplastic resin material should exhibit highflow and low viscosity when heated and extruded through the impregnationdie. It should not degrade when heated to temperatures in excess of themelt temperature which may be necessary to ensure complete impregnationof the fibers therewith. The first thermoplastic resin material may beselected from nylon 6, nylon 66, polyethylenes, polyacetals,polyphenylene sulfide, polyurethanes, polypropylene, polycarbonates,polyesters, acrylonitrile-butadiene-styrene, and combinations thereof.

The continuous lengths of fiber strands necessary to provide reinforcingqualities to the composite structure may be selected from glass,amorphous carbon, graphitic carbon, aramids, stainless steel, ceramics,alumina, titanium, magnesium, metal-coated carbons, rock wool andcombinations thereof. Typically, the fiber strands at the onset of themanufacturing process are typically about 6-11 millimeters in length.During the manufacturing process, the strands may break and range towithin about 2 to about 11 millimeters in length when the manufacturingprocess is complete or, more particularly, may range from about 6 to 11millimeters in length when the manufacturing process is complete.Generally, the strands, obtainable in bundles of many filaments onspools, are generally separated by the lobes within the impregnation dieand impregnated during the process. Optionally, the fiber strands may beheated prior to impregnation to increase strand separation from thebundle and improve impregnation.

The second thermoplastic resin material should be compatible with thefirst thermoplastic resin material. The two resins should exhibitcompatible coefficients of thermal expansion as well as bonding forcesso that the intermediate mixing zone is formed at the interface of theresins during the process of preparing the fiber reinforced blendmaterials. The coefficients of thermal expansion of the two resinmaterials should be within the same range of each other to ensure thatthe resin materials within the fiber reinforced blend materials willexpand and contract at the same rates. Otherwise, deformation of thefiber reinforced blend materials may occur. While the secondthermoplastic resin material may be selected from nylon 6, nylon 66,polyethylenes, polyacetals, polyphenylene sulfide, polyurethanes,polypropylene, polycarbonates, polyesters,acrylonitrile-butadiene-styrene, and combinations thereof, it is notessential that the first and second thermoplastic resin materials beidentical.

Additive materials may also be included in the fiber reinforcedthermoplastic blend. Additives are generally selected from componentsthat provide enhanced molding properties as well as physical andchemical properties of shaped articles prepared therefrom. It may bedesirable to add pigments to the fiber reinforced thermoplastic blend toreduce finishing labor of shaped articles. Since many additive materialare heat sensitive, an excessive amount of heat may cause them todecompose and produce volatile gases. Therefore, if a heat sensitiveadditive material is extruded with an impregnation resin under highheating conditions, the result may be a complete degradation of theadditive material. Additive materials of the invention may be selectedfrom mineral reinforcing agents, lubricants, blowing agents, foamingagents, heat sensitive pigments, and combinations thereof. The mineralreinforcing agents may be selected from calcium carbonate, silica, mica,clays, talc, calcium silicate, graphite, wollastonite, calcium silicate,alumina trihydrate, barium ferrite, and combinations thereof.

The first and second thermoplastic resin materials are polycarbonate andacrylonitrile-butadiene-styrene and the fiber reinforcement is glass.The fiber reinforcement material is present preferably about 40% byvolume of the total volume of the blend.

Referring back to FIGS. 1-3, the forceps 10 includes an end effectorassembly 100 which attaches to the distal ends 16 a and 16 b of shafts12 a and 12 b, respectively. As explained in more detail below, the endeffector assembly 100 includes pair of opposing jaw members 110 and 120which are pivotably connected about a pivot pin 65 and which are movablerelative to one another to grasp tissue.

Each shaft 12 a and 12 b includes a handle 15 and 17, respectively,disposed at the proximal end 14 a and 14 b thereof which each define afinger hole 15 a and 17 a, respectively, therethrough for receiving afinger of the user. As can be appreciated, finger holes 15 a and 17 afacilitate movement of the shafts 12 a and 12 b relative to one anotherwhich, in turn, pivot the jaw members 110 and 120 from an open positionwherein the jaw members 110 and 120 are disposed in spaced relationrelative to one another to a clamping or closed position wherein the jawmembers 110 and 120 cooperate to grasp tissue therebetween.

As best seen in FIG. 7, shaft 12 b is constructed from two components,namely, 12 b 1 and 12 b 2, which matingly engage one another about thedistal end 16 a of shaft 12 a to form shaft 12 b. It is envisioned thatthe two component halves 12 b 1 and 12 b 2 may be ultrasonically-weldedtogether at a plurality of different weld points or the component halves12 b 1 and 12 b 2 may be mechanically engaged in any other knownfashion, snap-fit, glued, screwed, etc. After component halves 12 b 1and 12 b 2 are welded together to form shaft 12 b, shaft 12 a is securedabout pivot 65 and positioned within a cut-out or relief 21 definedwithin shaft portion 12 b 2 such that shaft 12 a is movable relative toshaft 12 b. More particularly, when the user moves the shaft 12 arelative to shaft 12 b to close or open the jaw members 110 and 120, thedistal portion of shaft 12 a moves within cutout 21 formed withinportion 12 b 2. It is envisioned that configuring the two shafts 12 aand 12 b in the fashion facilitates gripping and reduces the overallsize of the forceps 10 which is especially advantageous during surgeriesin small cavities.

As best illustrated in FIG. 1, one of the shafts, e.g., 12 b, includes aproximal shaft connector 77 which is designed to connect the forceps 10to a source of electrosurgical energy such as an electrosurgicalgenerator (not shown). The proximal shaft connector 77electromechanically engages an electrosurgical cable 70 such that theuser may selectively apply electrosurgical energy as needed.Alternatively, the cable 70 may be feed directly into shaft 12 b.

As explained in more detail below, the distal end of the cable 70connects to a handswitch 50 to permit the user to selectively applyelectrosurgical energy as needed to seal tissue grasped between jawmembers 110 and 120. More particularly, the interior of cable 70 housesleads 71 a, 71 b and 71 c which upon activation of the handswitch 50conduct the different electrical potentials from the electrosurgicalgenerator to the jaw members 110 and 120 (See FIGS. 3 and 4). As can beappreciated, positioning the switch 50 on the forceps 10 gives the usermore visual and tactile control over the application of electrosurgicalenergy. These aspects are explained below with respect to the discussionof the handswitch 50 and the electrical connections associatedtherewith.

The two opposing jaw members 110 and 120 of the end effector assembly100 are pivotable about pin 65 from the open position to the closedposition for grasping tissue therebetween. Pivot pin 65 may consist oftwo component halves 65 a and 65 b which matingly engage and pivotablysecure the shafts 12 a and 12 b during assembly such that the jawmembers 110 and 120 are freely pivotable between the open and closedpositions. For example, the pivot pin 65 may be configured to be springloaded such that the pivot snap fits together at assembly to secure thetwo shafts 12 a and 12 b for rotation about the pivot pin 65.

The tissue grasping portions of the jaw members 110 and 120 aregenerally symmetrical and include similar component features whichcooperate to permit facile rotation about pivot pin 65 to effect thegrasping and sealing of tissue. As a result and unless otherwise noted,jaw member 110 and the operative features associated therewith areinitially described herein in detail and the similar component featureswith respect to jaw member 120 will be briefly summarized thereafter.Moreover, many of the features of the jaw members 110 and 120 aredescribed in detail in commonly-owned U.S. patent application Ser. Nos.10/284,562, 10/116,824, 09/425,696, 09/178,027 and PCT ApplicationSerial No. PCT/US01/11420 the contents of which are all herebyincorporated by reference in their entirety herein.

As best shown in FIGS. 14 and 15, jaw member 110 includes an insulatedouter housing 116 which is dimensioned to mechanically engage anelectrically conductive sealing surface 112. The outer insulativehousing 116 extends along the entire length of jaw member 110 to reducealternate or stray current paths during sealing and/or incidentalburning of tissue. The electrically conductive surface 112 conductselectrosurgical energy of a first potential to the tissue uponactivation of the handswitch 50. Insulated outer housing 116 isdimensioned to securely engage the electrically conductive sealingsurface 112. It is envisioned that this may be accomplished by stamping,by overmolding, by overmolding a stamped electrically conductive sealingplate and/or by overmolding a metal injection molded seal plate. Othermethods of affixing the seal surface 112 to the outer housing 116 aredescribed in detail in one or more of the above-identified references.The jaw members 110 and 120 are made form a conductive material andpowder coated with an insulative coating to reduce stray currentconcentrations during sealing.

It is also contemplated that the electrically conductive sealing surface112 may include an outer peripheral edge which has a radius and theinsulated outer housing 116 meets the electrically conductive sealingsurface 112 along an adjoining edge which is generally tangential to theradius and/or meets along the radius. At the interface, the electricallyconductive surface 112 may be raised relative to the insulated outerhousing 116. Alternatively, the jaw member 110 including the sealingplate 112 and the outer insulative housing 116 may be formed as part ofa molding process to facilitate manufacturing and assembly. These andother envisioned embodiments are discussed in commonly-owned, co-pendingPCT Application Serial No. PCT/US01/11412 and commonly owned, co-pendingPCT Application Serial No. PCT/US01/11411, the contents of both of theseapplications being incorporated by reference herein in their entirety.

The insulated outer housing 116 and the electrically conductive sealingsurface 112 may be dimensioned to limit and/or reduce many of the knownundesirable effects related to tissue sealing, e.g., flashover, thermalspread and stray current dissipation. All of the aforementioned andcross referenced manufacturing techniques produce an electrode having anelectrically conductive surface 112 which is substantially surrounded byan insulated outer housing 116.

Likewise, jaw member 120 includes similar elements which include: anouter housing 126 which engages an electrically conductive sealingsurface 122. The electrically conducive sealing surface 122 conductselectrosurgical energy of a second potential to the tissue uponactivation of the handswitch 50.

It is envisioned that one of the jaw members, e.g., 120, includes atleast one stop member 175 disposed on the inner facing surface of theelectrically conductive sealing surface 122 (and/or 112). Alternativelyor in addition, the stop member 175 may be positioned adjacent to theelectrically conductive sealing surfaces 112, 122 or proximate the pivotpin 65. The stop member(s) is designed to facilitate gripping andmanipulation of tissue and to define a gap “G” between opposing jawmembers 110 and 120 during sealing (See FIGS. 18 and 20). The separationdistance during sealing or the gap distance “G” is within the range ofabout 0.001 inches (˜0.03 millimeters) to about 0.006 inches (˜0.016millimeters).

A detailed discussion of these and other envisioned stop members 175 aswell as various manufacturing and assembling processes for attaching,disposing, depositing and/or affixing the stop members to theelectrically conductive sealing surfaces 112, 122 are described incommonly-assigned, co-pending PCT Application Serial No. PCT/US01/11222which is hereby incorporated by reference in its entirety herein.

As mentioned above, two mechanical factors play an important role indetermining the resulting thickness of the sealed tissue andeffectiveness of the seal, i.e., the pressure applied between opposingjaw members 110 and 120 and the gap “G” between the opposing jaw members110 and 120 (or opposing seal surfaces 112 and 122 during activation).It is known that the thickness of the resulting tissue seal cannot beadequately controlled by force alone. In other words, too much force andthe sealing surfaces 112 and 122 of the two jaw members 110 and 120would touch and possibly short resulting in little energy travelingthrough the tissue thus resulting in a bad seal. Too little force andthe seal would be too thick. Applying the correct force is alsoimportant for other reasons: to oppose the walls of the vessel; toreduce the tissue impedance to a low enough value that allows enoughcurrent through the tissue; and to overcome the forces of expansionduring tissue heating in addition to contributing towards creating therequired end tissue thickness which is an indication of a good seal.

The seal surfaces 112 and 122 are relatively flat to avoid currentconcentrations at sharp edges and to avoid arcing between high points.In addition and due to the reaction force of the tissue when engaged,jaw members 110 and 120 may be manufactured to resist bending, i.e.,tapered along their length which provides a constant pressure for aconstant tissue thickness at parallel and the thicker proximal portionof the jaw members 110 and 120 will resist bending due to the reactionforce of the tissue.

As best seen in FIGS. 9 and 14, the jaw members 110 and 120 include aknife channel 115 disposed therebetween which is configured to allowreciprocation of a cutting mechanism 80 therewithin. One example of aknife channel is disclosed in commonly-owned U.S. patent applicationSer. No. 10/284,562 the entire contents of which are hereby incorporatedby reference herein. The complete knife channel 115 is formed when twoopposing channel halves 115 a and 115 b associated with respective jawmembers 110 and 120 come together upon grasping of the tissue. It isenvisioned that the knife channel 115 may be tapered or some otherconfiguration which facilitates or enhances cutting of the tissue duringreciprocation of the cutting mechanism 80 in the distal direction.Moreover, the knife channel 115 may be formed with one or more safetyfeatures which prevent the cutting mechanism 80 from advancing throughthe tissue until the jaw members 110 and 120 are closed about thetissue.

The arrangement of shaft 12 b is slightly different from shaft 12 a.More particularly, shaft 12 b is generally hollow to define a chamber 28therethrough which is dimensioned to house the handswitch 50 (and theelectrical components associated therewith), the actuating mechanism 40and the cutting mechanism 80. As best seen in FIGS. 3, 4 and 7, theactuating mechanism 40 includes a rack and pinion system having firstand second gear tracks 42 and 86, respectively, and a pinion to advancethe cutting mechanism 80. More particularly, the actuating mechanism 40includes a trigger or finger tab 43 which is operatively associated witha first gear rack 42 such that movement of the trigger or finger tab 43moves the first rack 42 in a corresponding direction. The actuatingmechanism 40 mechanically cooperates with a second gear rack 86 which isoperatively associated with a drive rod 89 and which advances the entirecutting mechanism 80 as will be explained in more detail below. Driverod 89 includes a distal end 81 which is configured to mechanicallysupport the cutting blade 87 and which acts as part of a safety lockoutmechanism as explained in more detail below.

Interdisposed between the first and second gear racks 42 and 86,respectively, is a pinion gear 45 which mechanically meshes with bothgear racks 42 and 86 and converts proximal motion of the trigger 43 intodistal translation of the drive rod 89 and vice versa. Moreparticularly, when the user pulls the trigger 43 in a proximal directionwithin a predisposed channel 29 in the shaft 12 b (See arrow “A” in FIG.23), the first rack 42 is translated proximally which, in turn, rotatesthe pinion gear 45 in a counter-clockwise direction. Rotation of thepinion gear 45 in a counter-clockwise direction forces the second rack86 to translate the drive rod 89 distally (See arrow “B” in FIG. 23)which advances the blade 87 of the cutting mechanism 80 through tissue400 grasped between jaw members 110 and 120, i.e., the cutting mechanism80, e.g., knife, blade, wire, etc., is advanced through channel 115 upondistal translation of the drive rod 89.

It is envisioned that multiple gears or gears with different gear ratiosmay be employed to reduce surgical fatigue which may be associated withadvancing the cutting mechanism 80. In addition, it is contemplated thegear tracks 42 and 86 are configured to include a plurality of gearteeth tracks 43 and 87, respectively, which may be of different lengthto provide additional mechanical advantage for advancing the jaw members110 and 120 through tissue. The rack and pinion arrangement may becurved for spatial purposes and to facilitate handling and/or to enhancethe overall ergonomics of the forceps 10.

A spring 83 may be employed within chamber 28 to bias the first rack 42upon proximal movement thereof such that upon release of the trigger 43,the force of the spring 83 automatically returns the first rack 42 toits distal most position within channel 29. Obviously, spring 83 may beoperatively connected to bias the second rack 86 to achieve the samepurpose.

The trigger 43 includes one or more ergonomically friendly featureswhich enhance the tactile feel and grip for the user to facilitateactuation of the finger tab 43. Such features may include, raisedprotuberances, rubber inserts, scallops and gripping surfaces and thelike. In addition, the downward orientation of the trigger 43 isbelieved to be particularly advantageous since this orientation tends tominimize accidental or inadvertent activation of the trigger 43 duringhandling. Moreover, it is contemplated that integrally associating(molding or otherwise forming) the trigger 43 and the gear rack 42during the manufacturing process minimizes the number of parts which, inturn, simplifies the overall assembly process.

As best seen in FIGS. 5, 9, 10, 11, 12, 17, 20 and 23, a safety lockoutmechanism 200 is associated with the actuating assembly 40 and thecutting mechanism 80 to prevent advancement of the cutting mechanism 80until the jaw members 110 and 120 are positioned and closed abouttissue. Other lockout mechanisms and features are described incommonly-owned U.S. application Ser. Nos. 10/460,926, 10/461,550,10/462,121 and U.S. Provisional Application Ser. No. 60/523,387 whichare all incorporated by reference herein in their entirety. The safetylockout mechanism includes a series of inter-cooperating elements whichwork together to prevent unintentional firing of the cutting mechanism80 when the jaw members 110 and 120 are disposed in the open position.

More particularly, the distal end 81 of the cutting mechanism 80 isdimensioned to reciprocate within a channel 126 b defined in theproximal end of jaw member 120 when jaw member 110 and 120 are disposedin a closed position (see FIG. 9). The proximal end of channel 126 bdefines a recess or relieved portion 123 therein which includes aforward stop 129 which abuts and prevents advancement of the distal end81 of the cutting mechanism 80 when the jaw members 110 and 120 aredisposed in the open position (See FIGS. 9 and 17). The proximal portionof jaw member 120 also includes a guide slot 124 defined therethroughwhich allows a terminal connector 150 or so called “POGO” pin to ridetherein upon movement of the jaw members 110 and 120 from the open toclosed positions (See FIGS. 17 and 24). In addition, the proximal endincludes an aperture 125 defined therethrough which houses the pivot pin65. Jaw member 110 also includes a channel 126 a which aligns withchannel 126 b when the jaw members 110 and 120 are disposed in theclosed position about tissue.

As best shown in FIGS. 17 and 24 which show the jaw members 110 and 120in open and closed orientations, respectively, the operation of thelockout mechanism 200 is easily described. When jaw member 120 isrotated with respect to jaw member 110 about pivot 65 a flanged portion81 a of the distal end 81 of cutting mechanism 80 is slidinglyincorporated within recess 123 and against stop 129 located in theproximal end of jaw member 120 (See FIG. 12). The stop 129 prevents thecutting mechanism 80 from moving forward due to unintentional actuationof the trigger 43. At the same time, the terminal connector 150 movesfreely within slot 124 upon rotation of the jaw members 110 and 120. Itis envisioned that the terminal connector 150 is seated within aperture151 within jaw member 110 and rides within slot 124 of jaw member 120 toprovide a “running” or “brush” contact to supply electrosurgical energyto jaw member 120 during the pivoting motion of the forceps 10 (See FIG.17). Recess 123 also includes a rim or flange 199 which preventsover-rotation of shaft 12 a relative to shaft 12 b. More particularlyand as best seen on FIGS. 9 and 17, flange 199 is dimensioned to abut astop 201 disposed within forceps 110 when rotated to a fully openposition to prevent unintentional over-rotation of the forceps 10.

When the jaw members 110 and 120 are moved to the closed position asillustrated in FIG. 24, the safety lockout mechanism 200 automaticallydisengages to allow distal advancement of the cutting mechanism 80. Moreparticularly, when the jaw members 110 and 120 are closed about tissue,the distal end 81 including the flanged portion 81 a automaticallyaligns within the channels 126 a and 126 of jaw members 110 and 120,respectively, to allow selective actuation of the cutting mechanism 80.As shown in FIG. 24, the distal end 81 advances through channel 126 aand 126 b forcing the knife blade 87 through knife channel 115 (115 aand 115 b) to cut tissue. As described above, when the actuating flange43 is released, spring 83 biases the drive rod 89 back to theproximal-most position (not shown) which, in turn, re-aligns distal end81 with recess 123 to allow the jaw members 110 and 120 to be moved tothe open position to release the tissue 400.

It is envisioned that the safety lockout mechanism 200 may include oneor more electrical or electromechanical sensors (not shown) whichprevent the cutting mechanism 80 from advancing through tissue until atissue seal has been created. For example, the safety lockout mechanism200 could include a sensor which upon completion of a tissue sealactivates a switch or release (not shown) which unlocks the cuttingmechanism 80 for advancement through tissue.

As best seen in FIGS. 9 and 10, blade 87 is flexible so it easilyadvances through the curved knife channel 115. For example, upon distaladvancement of the cutting mechanism 80, the cutting blade 87 willsimply flex and ride around the knife channel 115 through the tissue 400held between jaw members 110 and 120. A curved blade (not shown) mayalso be utilized which has a similar radius of curvature as the knifechannel 115 such that the blade will travel through the knife channel115 without contacting the surfaces of the knife channel 115.

FIGS. 1, 2 and 19 show a ratchet 30 for selectively locking the jawmembers 110 and 120 relative to one another in at least one positionduring pivoting. A first ratchet interface 31 a extends from theproximal end 14 a of shaft member 12 a towards a second ratchetinterface 31 b on the proximal end 14 b of shaft 12 b in generalvertical registration therewith such that the inner facing surfaces ofeach ratchet 31 a and 31 b abut one another upon closure of the jawmembers 110 and 120 about the tissue 400. It is envisioned that eachratchet interface 31 a and 31 b may include a plurality of step-likeflanges (not shown) which project from the inner facing surface of eachratchet interface 31 a and 31 b such that the ratchet interfaces 31 aand 31 b interlock in at least one position. Each position associatedwith the cooperating ratchet interfaces 31 a and 31 b holds a specific,i.e., constant, strain energy in the shaft members 12 a and 12 b which,in turn, transmits a specific closing force to the jaw members 110 and120. It is envisioned that the ratchet 30 may include graduations orother visual markings which enable the user to easily and quicklyascertain and control the amount of closure force desired between thejaw members. It is envisioned that the shafts 12 a and 12 b may bemanufactured from a particular plastic material which is tuned to applya particular closure pressure within the above-specified working rangeto the jaw members 110 and 120 when ratcheted. As can be appreciated,this simplified the manufacturing process and eliminates underpressurizing and over pressurizing the jaw member s 110 and 120 duringthe sealing process. The proximal connector 77 may include a stop orprotrusion 63 (See FIG. 7) which prevents the user from overpressurizing the jaw members 110 and 120 by squeezing the handle 15 and17 beyond the ratchet positions.

It is envisioned that by making the forceps 10 disposable, the forceps10 is less likely to become damaged since it is only intended for asingle use and, therefore, does not require cleaning orre-sterilization. As a result, the functionality and consistency of thevital sealing components, e.g., the conductive surfaces 112 and 122, thestop member(s) 175, and the insulative housings 126 and 116 will assurea uniform and quality seal.

FIGS. 3 and 4 show the electrical details relating to the switch 50.More particularly and as mentioned above, cable 70 includes threeelectrical leads 71 a, 71 b and 71 c which are fed through shaft 12 b.The electrosurgical cable 70 is fed into the bottom of shaft 12 b and isheld securely therein by one or more mechanical interfaces (not shown).Lead 71 c extends directly from cable 70 and connects to jaw member 120to conduct the second electrical potential thereto. Leads 71 a and 71 bextend from cable 70 and connect to a circuit board 52.

Several different types of handswitches 50 are envisioned, for example,switch 50 is a regular push-button style switch but may be configuredmore like a toggle switch which permits the user to selectively activatethe forceps 10 in a variety of different orientations, i.e.,multi-oriented activation, which simplifies activation. One particulartype of handswitch is disclosed in commonly-owned, co-pending U.S.patent application Ser. No. 10/460,926 the contents of which are herebyincorporated by reference herein.

The electrical leads 71 a and 71 b are electrically connected to thecircuit board 52 such that when the switch 50 is depressed, a triggerlead 72 carries the first electrical potential from the circuit board 52to jaw member 110. As mentioned above, the second electrical potentialis carried by lead 71 c directly from the generator (not shown) to jawmember 120 through the terminal connector 150 as described above. It isenvisioned that a safety switch or circuit (not shown) may be employedsuch that the switch 50 cannot fire unless the jaw members 110 and 120are closed and/or unless the jaw members 110 and 120 have tissue 400held therebetween. In the latter instance, a sensor (not shown) may beemployed to determine if tissue is held therebetween. In addition, othersensor mechanisms may be employed which determine pre-surgical,concurrent surgical (i.e., during surgery) and/or post surgicalconditions. The sensor mechanisms may also be utilized with aclosed-loop feedback system coupled to the electrosurgical generator toregulate the electrosurgical energy based upon one or more pre-surgical,concurrent surgical or post surgical conditions. Various sensormechanisms and feedback systems are described in commonly-owned,co-pending U.S. patent application Ser. No. 10/427,832 the entirecontents of which are hereby incorporated by reference herein.

As best shown in FIGS. 1, 2 and 7, a switch cap 53 is positioned inelectromechanical communication with the circuit board 52 along one sideof shaft 12 b to facilitate activation of switch 50. As can beappreciated, the position of the switch cap 53 enables the user toeasily and selectively energize the jaw members 110 and 120 with asingle hand. It is envisioned that the switch cap 53 may behermetically-sealed to avoid damage to the circuit board 52 during wetoperating conditions. In addition, it is contemplated that bypositioning the switch cap 53 at a point distal to the actuatingassembly 40, the overall sealing process is greatly simplified andergonomically advantageous to the surgeon, i.e., after activation, thesurgeon's finger is automatically poised for actuation of the actuatingassembly 40 to advance the cutting mechanism 80. The geometry alsodisallows inadvertent actuation of the forceps 10 when the forceps 10 isnot activated or “powered down”.

The jaw members 110 and 120 are electrically isolated from one anothersuch that electrosurgical energy can be effectively transferred throughthe tissue to form a tissue seal. Each jaw member, e.g., 110, includes auniquely-designed electrosurgical cable path disposed therethrough whichtransmits electrosurgical energy to the electrically conductive sealingsurface 112. It is envisioned that the jaw members 110 and 120 mayinclude one or more cable guides or crimp-like electrical connectors todirect the cable leads towards electrically conductive sealing surfaces112 and 122. Cable leads may be held securely along the cable path topermit pivoting of the jaw members 110 and 120 about pivot 65.

As best shown in FIG. 7, the cable leads 71 a, 71 b and 71 c areprotected by two insulative layers, an outer protective sheath whichsurrounds all three leads 71 a, 71 b and 71 c and a secondary protectivesheath which surrounds each individual cable lead, 71 a, 71 b and 71 c,respectively. The two electrical potentials are isolated from oneanother by virtue of the insulative sheathing surrounding each cablelead 71 a, 71 b and 71 c.

In operation, the surgeon simply utilizes the two opposing handlemembers 15 and 17 to grasp tissue between jaw members 110 and 120. Thesurgeon then activates the handswitch 50 to provide electrosurgicalenergy to each jaw member 110 and 120 to communicate energy through thetissue held therebetween to effect a tissue seal (See FIGS. 21 and 22).Once sealed, the surgeon activates the actuating mechanism 40 to advancethe cutting blade 87 through the tissue to sever the tissue 400 alongthe tissue seal (See FIG. 25).

From the foregoing and with reference to the various figure drawings,those skilled in the art will appreciate that certain modifications canalso be made to the present disclosure without departing from the scopeof the same. For example, although the electrical connections aretypically incorporated within one shaft 12 b and the forceps 10 isintended for right-handed use, it is contemplated the electricalconnections may be incorporated within the other shaft 12 a dependingupon a particular purpose and/or to facilitate manipulation by aleft-handed user. Alternatively, the forceps 10 may operated in anupside down orientation for left-handed users without compromising orrestricting any operating characteristics of the forceps 10.

It is also contemplated that the forceps 10 (and/or the electrosurgicalgenerator used in connection with the forceps 10) may include a sensoror feedback mechanism (not shown) which automatically selects theappropriate amount of electrosurgical energy to effectively seal theparticularly-sized tissue grasped between the jaw members 110 and 120.The sensor or feedback mechanism may also measure the impedance acrossthe tissue during sealing and provide an indicator (visual and/oraudible) that an effective seal has been created between the jaw members110 and 120. Commonly-owned U.S. patent application Ser. No. 10/427,832discloses several different types of sensory feedback mechanisms andalgorithms which may be utilized for this purpose. The contents of thisapplication are hereby incorporated by reference herein.

Experimental results suggest that the magnitude of pressure exerted onthe tissue by the sealing surfaces of the jaw members 110 and 120 isimportant in assuring a proper surgical outcome. Tissue pressures withina working range of about 3 kg/cm² to about 16 kg/cm² and, preferably,within a working range of 7 kg/cm² to 13 kg/cm² have been shown to beeffective for sealing arteries and vascular bundles. Tissue pressureswithin the range of about 4 kg/cm² to about 10 kg/cm² have proven to beparticularly effective in sealing arteries and tissue bundles. Theinter-engaging surfaces 31 a and 31 b of the ratchet 30 may bepositioned to provide a closure within this working range. In additionand if the ratchet 30 includes multiple positions as explained above, itis envisioned that each particular ratchet position employs a specificclosure force on tissue for particular surgical purposes. For example,the shafts 12 a and 12 b may be manufactured such that the springconstants of the shaft portions 12 a and 12 b, in conjunction with theplacement of the ratchet interfaces 31 a and 31 b, will yield pressureswithin the above working range. The successive positions of the ratchetinterfaces 21 a and 31 b (and any other positions as described above)increase the closure force between opposing sealing surfaces 112 and 122incrementally within the above working range.

It is also envisioned that the drive rod 89 may be connected to the sameor alternate source of electrosurgical energy and may be selectivelyenergizable by the surgeon during cutting. As can be appreciated, thiswould enable the surgeon to electrosurgically cut the tissue along thetissue seal. As a result thereof, a substantially dull blade may beemployed to electrosurgically cut the tissue. It is also envisioned thata substantially dull blade may be utilized with a spring loaded cuttingmechanism which, due to the clamping pressure between the opposing jawmembers 110 and 120 and due to the force at which the spring-loadedcutting mechanism advances the blade, the tissue will sever along thetissue seal.

It is also contemplated that the forceps may include a safety bladereturn mechanism (not shown). For example and as mentioned above, thecutting blade 80 may include one or more springs which automaticallyreturn the cutting blade 87 after actuation of the actuator 40. Inaddition, a manual return may be included which allows the user tomanually return the blade 87 if the automatic blade return (e.g.,spring) should fail due to sticking, skewing, or some other unforeseensurgical condition. Alternatively, the actuating mechanism 40 may bespring-loaded and advanced automatically when tab 43 is depressed by thesurgeon. After deployment, the surgeon manually retracts the switch 43to reset the switch 43 and cutting mechanism 80 for subsequentdeployment.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

1. A disposable open electrosurgical forceps for sealing tissue,comprising: a pair of first and second shaft members, each shaft memberhaving a jaw member disposed at a distal end thereof, the jaw membersbeing movable from an open position in spaced relation relative to oneanother to at least one subsequent closed position wherein the jawmembers cooperate to grasp tissue therebetween; each of the jaw membersincluding an electrically conductive sealing plate for communicatingelectrosurgical energy through tissue held therebetween; at least one ofthe jaw members including a curved knife channel defined along a lengththereof, the curved knife channel being dimensioned to reciprocate aflexible blade therealong; at least one of the shafts including alongitudinal channel disposed therein; a cutting mechanism operativelyconnected to one of the shaft members, the cutting mechanism beingconfigured to selectively advance the flexible blade from a firstposition wherein the flexible blade is disposed proximal to tissue heldbetween the jaw members to at least one subsequent position wherein theflexible blade is disposed distal to tissue held between the jawmembers, the cutting mechanism including a trigger in slidablecommunication with the longitudinal channel which cooperates with a rackand pinion system to advance the flexible blade from the first to secondpositions through tissue held therebetween; and a lockout mechanismincluding: a recess defined at a proximal end of the longitudinalchannel; a positive stop defined at a distal edge of the recess; whereinthe positive stop is configured to engage a distal end of the cuttingmechanism to prevent distal advancement of the flexible blade when thejaw members are in an open position and to allow distal advancement ofthe flexible blade when the jaw members are in a subsequent closedposition; and at least one sensor configured to prevent the flexibleblade from advancing through tissue until tissue is sealed.
 2. Thedisposable endoscopic bipolar forceps in accordance with claim 1,wherein the first and second shaft members contain a fiber reinforcedthermoplastic blend material including fiber strands in the range ofabout 2 millimeters to about 11 millimeters in length.
 3. The disposableendoscopic bipolar forceps in accordance with claim 1, wherein the firstand second shaft members contain a fiber reinforced thermoplastic blendmaterial including fiber strands in the range of about 6 millimeters toabout 11 millimeters in length.
 4. The disposable endoscopic bipolarforceps in accordance with claim 2, wherein the fiber reinforcedthermoplastic blend material is a blend of at least one firstthermoplastic resin material and at least one second thermoplastic resinmaterial.
 5. The disposable endoscopic bipolar forceps in accordancewith claim 4, wherein the at least one first thermoplastic resinmaterial is polycarbonate.
 6. The disposable endoscopic bipolar forcepsin accordance with claim 4, wherein the at least one secondthermoplastic resin material is acrylonitrile-butadiene-styrene.
 7. Thedisposable endoscopic bipolar forceps in accordance with claim 2,wherein the fiber reinforced thermoplastic blend material is a blend ofpolycarbonate and acrylonitrile-butadiene-styrene.
 8. The disposableendoscopic bipolar forceps in accordance with claim 2, wherein the fiberreinforced thermoplastic blend material contains glass fiber.
 9. Thedisposable endoscopic bipolar forceps in accordance with claim 7,wherein the fiber reinforced thermoplastic blend material contains glassfiber present in an amount of about 40% by volume of the total volume ofthe blend.
 10. A disposable open electrosurgical forceps for sealingtissue, comprising: a pair of first and second shaft members containinga glass fiber reinforced blend of polycarbonate resin material andacrylonitrile-butadiene-styrene resin material having glass fibers inthe range of about 2 millimeters to about 11 millimeters in length andwhich make up about 40% by volume of the total volume of the blend, eachshaft member having a jaw member disposed at a distal end thereof, thejaw members being movable from an open position in spaced relationrelative to one another to at least one subsequent closed positionwherein the jaw members cooperate to grasp tissue therebetween; each ofthe jaw members including an electrically conductive sealing plate forcommunicating electrosurgical energy through tissue held therebetween;at least one of the jaw members including a curved knife channel definedalong a length thereof, the curved knife channel being dimensioned toreciprocate a flexible blade therealong; at least one of the shaftsincluding a longitudinal channel disposed therein; a cutting mechanismoperatively connected to one of the shaft members, the cutting mechanismbeing configured to selectively advance the flexible blade from a firstposition wherein the flexible blade is disposed proximal to tissue heldbetween the jaw members to at least one subsequent position wherein theflexible blade is disposed distal to tissue held between the jawmembers, the cutting mechanism including a trigger in slidablecommunication with the longitudinal channel which cooperates with a rackand pinion system to advance the flexible blade from the first to secondpositions through tissue held therebetween; and a lockout mechanismincluding: a recess defined at a proximal end of the longitudinalchannel; a positive stop defined at a distal edge of the recess; whereinthe positive stop is configured to engage a distal end of the cuttingmechanism to prevent distal advancement of the flexible blade when thejaw members are in an open position and to allow distal advancement ofthe flexible blade when the jaw members are in a subsequent closedposition; and at least one sensor configured to prevent the flexibleblade from advancing through tissue until tissue is sealed.
 11. Thedisposable endoscopic bipolar forceps in accordance with claim 10,wherein the fiber reinforced thermoplastic blend material includes fiberstrands in the range of about 6 millimeters to about 11 millimeters inlength.
 12. The disposable endoscopic bipolar forceps in accordance withclaim 10, wherein the fiber reinforced thermoplastic blend material is ablend of at least one first thermoplastic resin material and at leastone second thermoplastic resin material.
 13. The disposable endoscopicbipolar forceps in accordance with claim 12, wherein the at least onefirst thermoplastic resin material is polycarbonate.